1. Field of the Invention
The present invention relates to enclosures for telecommunications applications, and, in particular, to enclosures for receiving hardware for splicing and/or connecting to cables carrying telecommunications signals, such as telephone cables carrying telephone signals.
2. Description of the Related Art
A building entrance protector (BEP) enclosure houses the physical interface between the nodes of a local telecommunications network and a telecommunications cable. For example, a BEP enclosure may house the interface hardware between the telephones of an office building and an exterior telephone cable having a number of twisted copper pairs that carry the voice signals for those telephones. A BEP enclosure would typically be mounted in the basement or first floor of the office building. A BEP enclosure may also be used to house the interface hardware for systems based on fiber optical communications. Similarly, BEP enclosures may be used with telecommunications systems carrying signals other than just telephone voice signals.
A BEP enclosure provides two main functions: (1) it houses the hardware that provides connections between a cable and the individual nodes (e.g., telephones) of a local network; and (2) it houses the hardware that provides electrical isolation between the cable and the local network. Electrical isolation is intended to prevent any high voltages and/or high currents that may exist from time to time in the cable from reaching the local network. For example, a BEP enclosure will house isolation components designed to protect telephone users from lightning striking a telephone cable. Such electrical isolation is typically provided by 5-pin plug-in protectors that quickly connect signals to ground upon detection of sufficiently high voltages or currents.
Depending on the situation, it may be desirable to control the access that different users have to the different types of hardware housed in a BEP enclosure. For example, when a BEP enclosure is to be used in an office building, it may be desirable to provide operators of the office building with access to the connection hardware housed in the BEP enclosure, but not to the isolation hardware. In this way, the office-building operators would be able to adjust the distribution of telephone signals from the cable to the various offices in the building, while, at the same time, being prevented from disturbing the electrical isolation hardware housed in the BEP enclosure.
To achieve this access control, BEP enclosures typically have two or more chambers that house the different types of hardware. For example, isolation components may be housed in a first chamber, and connection components, in a second chamber. The BEP enclosure can then be configured to provide only limited access to the office-building operators, that is, access to the second chamber but not to the first chamber. Representatives of the telephone service company, on the other hand, would have access to both chambers.
FIGS. 1(a) and 1(b) show perspective and cross-sectional views, respectively, of the three basic parts of a conventional BEP enclosure 100: the base 102, the mid layer 104, and the cover 106. The base is essentially a rectilinear box with a bottom, four side walls, and open on its top. The mid layer has four side walls with a mounting plane 108 perpendicular to the four side walls. The mid layer is adapted to be pivotally connected to the base at one side (110), and the cover is adapted to be pivotally connected to the mid layer at the other side (112). The interior of the base and the lower portion of the mid layer form an inner chamber 114 of the BEP enclosure, while the upper portion of the mid layer and the cover form an outer chamber 116 of the BEP enclosure. As such, the mounting plane of the mid layer forms both the top surface of the inner chamber and the bottom surface of the outer chamber.
Chamber access is typically controlled by the type of mechanism used to hold together the parts that form the chamber. For example, special security screws can be used to seal a chamber, thereby restricting access to only those individuals who have special tools designed to remove those security screws. Two such screws are 216-type screws and KS-type screws, each of which requires a different special tool to remove. If a regular slotted or Philips-head screw is used to secure the chamber, then access will not be restricted because regular and Philips-head screw drivers are readily available.
In certain circumstances, the hardware to be housed in the chambers of a BEP enclosure may change over time. For example, it may be desirable to replace one type of plug-in protector, used to provide high voltage/current electrical isolation and mounted to the bottom of the mounting plane within the inner chamber, with a faster, more reliable type of plug-in protector. Unfortunately, there may not be enough room in the inner chamber to add the improved protectors, which may be longer than the protectors that are to be replaced.